1. Field of the Invention
The present invention relates to a motor control device to which power is supplied from a control power source configured to supply power to a peripheral of a motor in order to control the motor driven by power stored in a DC link part connected to an alternating-current power source via a converter.
2. Description of Related Art
A motor control device for controlling a motor in order to carry out at least one of an operation to retract a driven object connected to the motor to a region where the driven object does not interfere with an object and an operation to stop the motor in order to avoid interference of the driven object connected to the motor with the object when power fails in a machine, such a machine tool, in which it is necessary to carry out a synchronized operation of a work and a tool therein at all times, is proposed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 8-54914 (JP8-54914A) and Japanese Unexamined Patent Publication (Kokai) No. 2011-209936 (JP2011-209936A).
However, there may be a case where it is not possible to secure power necessary for control by a motor control device to carry out at least one of the operation to retract a driven object connected to a motor to a region where the driven object does not interfere with an object and the operation to stop the motor in order to avoid interference of the driven object connected to the motor with the object.
On the other hand, a control device that secures power of a control device when power fails by an uninterruptible power source device is proposed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 5-333969 (JP5-333969A). However, the uninterruptible power source device is expensive, and therefore, if the uninterruptible power source device is used in order to secure power of the control device when power fails, there is such a disadvantage that the system including the control device is expensive.
Further, a motor control device that uses a control power source having a smoothing capacitor in order to secure power of the motor control device when power fails without raising the cost of the system including the motor control device is proposed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 10-263973 (JP10-263973A) and Japanese Unexamined Patent Publication (Kokai) No. 2004-216829 (JP2004-216829A).
However, power that the control power source having a smoothing capacitor can secure when power fails is smaller than power that the uninterruptible power source device can secure. Consequently, in the case where the control power source supplies power to a peripheral (motor cooling fan, monitor, etc.) of the motor in addition to the motor control device, there may be a case where it is not possible to secure power necessary for the control by the motor control device to carry out at least one of the operation to retract a driven object connected to the motor to a region where the driven object does not interfere with an object and the operation to stop the motor in order to avoid interference of the driven object connected to the motor with the object.
Further, as a motor control device using a control power source having a smoothing capacitor, a motor control device that lengthens the output hold time of the control power source by stopping supply of power to a peripheral of a motor in order to save parameters, operation values, etc., in a memory when power fails is proposed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 2007-185018 (JP2007-185018A).
The conventional motor control device that lengthens the output hold time of the control power source when power fails in order to save parameters, operation values, etc., in a memory when power fails is configured to stop supply of power to the peripheral of the motor even if first power necessary to retract a driven object connected to the motor to a region where the driven object does not interfere with an object, or second power necessary to stop the motor in order to avoid interference of the driven object connected to the motor with the object, or the sum of the first power and the second power cannot be secured, and therefore, it is not possible to lengthen the output hold time of the control power source in order to make it possible to carry out at least one of the operation to retract the driven object connected to the motor to a region where the driven object does not interfere with the object and the operation to stop the motor in order to avoid interference of the driven object connected to the motor with the object.